<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1{
            width: 200px;height: 200px;
            /*边框样式多样，具体参考学习文档*/
            border: 10px inset red;
        /*    圆角，值越大越圆*/
            border-radius: 50px;

        }
        #d2{
            width: 200px;
            height: 200px;
            border: 1px solid red;
            /*加内边距，会让框变大*/
            padding-left: 100px;
            padding-top: 100px;
        /*    取消影响*/
            box-sizing: border-box;

        }
    </style>
</head>
<body>
<div id="d2">内边距测试</div>
<div id="d1">边框测试</div>
</body>
</html>